BGCSE Biology 0572 flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Prokaryotic cell

A cell lacking a membrane-bound nucleus and membrane-bound organelles, such as a bacterium, whose genetic material lies free in the cytoplasm as a single loop.

Osmosis

The net movement of water molecules through a partially permeable membrane from a region of higher water concentration to a region of lower water concentration.

Active transport

Movement of dissolved substances across a cell membrane against a concentration gradient, using energy released by respiration and carrier proteins.

Enzyme specificity

Each enzyme has an active site shaped to fit only its particular substrate, so a given enzyme catalyses only one type of reaction.

Villi

Finger-like projections of the small intestine wall that greatly increase the surface area for absorption and contain a rich blood supply.

Bile

A green alkaline liquid made in the liver and stored in the gall bladder that emulsifies fats and neutralises acid from the stomach.

Balanced diet

A diet supplying all required nutrients in correct proportions: carbohydrates, proteins, lipids, vitamins, minerals, water and fibre.

Aerobic respiration

The release of energy from glucose using oxygen, producing carbon dioxide and water, and occurring mainly inside mitochondria.

Alveolus

A tiny air sac in the lung with a thin moist wall and surrounding capillaries, giving a large surface area for gas exchange.

Anaerobic respiration

Release of energy from glucose without oxygen, producing lactic acid in muscles or ethanol and carbon dioxide in yeast.

Transpiration

Loss of water vapour from leaf surfaces through stomata, which draws water up the xylem from the roots.

Double circulation

A system in which blood passes through the heart twice per complete circuit, once to the lungs and once to the body.

Red blood cell

A biconcave cell without a nucleus that contains haemoglobin, which combines with oxygen in the lungs and releases it in tissues.

Homeostasis

Maintenance of a constant internal environment around a set point, using negative feedback to correct any deviation.

Excretion

Removal of metabolic waste products such as carbon dioxide and urea from the body, distinct from removal of undigested food.

Negative feedback

A control mechanism in which a change from the set point triggers a response that reverses the change and restores the norm.

Reflex arc

The pathway of a reflex action: receptor, sensory neurone, relay neurone, motor neurone and effector, bypassing conscious thought.

Synapse

A small gap between two neurones across which an impulse travels by diffusion of a chemical transmitter, allowing one-way transmission.

Tropism

A directional growth response of a plant toward or away from a stimulus such as light or gravity, controlled by auxin distribution.

Hormone

A chemical secreted by an endocrine gland into the blood, carried to a target organ where it alters activity.

Insulin

A hormone from the pancreas that lowers blood glucose by increasing uptake by cells and storage as glycogen in the liver.

Adrenaline

A hormone from the adrenal glands that raises heart rate, breathing rate and blood glucose, preparing the body for action.

Placenta

An organ in the uterus where maternal and fetal blood come close, allowing exchange of nutrients, oxygen and waste without mixing.

Ovulation

Release of a mature egg from an ovary, usually around the middle of the menstrual cycle, making fertilisation possible.

Pollination

Transfer of pollen from an anther to a stigma, by wind or animals, bringing the male gamete to the female part.

Allele

One of the alternative forms of a gene, such as the dominant or recessive version, that occupies the same position on a chromosome.

Phenotype

The observable characteristics of an organism, resulting from its genotype interacting with the environment.

Mutation

A random change in the base sequence of DNA that may produce a new allele and so increase genetic variation.

Food chain

A sequence of organisms showing the transfer of energy from a producer through successive consumers, with arrows in the direction of transfer.

Decomposer

An organism such as a bacterium or fungus that breaks down dead material, releasing minerals back into the soil.

Binomial name

The two-part scientific name of a species, consisting of the genus with a capital letter and the species in lower case.

Dichotomous key

A series of paired contrasting statements, each offering two choices, used to identify an unknown organism step by step.